Pipelines are commonly used to transport fluids, both liquids and gases. Millions of miles of pipeline deliver fluids from a point of origin to a point of destination. Two commonly used pipelines are the pipelines that deliver natural gas and liquid petroleum (LP) gas to homes for use in appliances, such as heaters and clothes dryers. The natural gas and LP gas pipelines are two of the most indispensable pipelines in use today.
Both the natural gas and LP gas pipeline are sources of potential disaster if there is a leaky appliance or a catastrophic pipeline failure that causes gas to discharge into the atmosphere. Gas appliances, such as stoves, dryers, and heaters, are known to malfunction in ways that cause gas discharges into homes. Catastrophic pipeline failures usually occur during earthquakes or when earth-moving equipment accidentally strikes a pipeline.
After a gas leak in an appliance or a catastrophic pipeline failure, the flow of gas typically continues until a service worker shuts off the flow of gas by operating a valve upstream of the gas leak. In the meantime, the gas has discharged into the open air or a confined space, such as a home. Discharges into the air are undesirable because such discharges add pollutants to the atmosphere. Discharges of natural gas into a confined space can create deadly accumulations of natural gas that may result in fires and explosions. Because LP gas is heavier than air, discharges of LP gas are dangerous whether the LP gas is discharged into the atmosphere or into a confined space.
It is well known that devices already exist for protecting a house from an overload of electrical current, namely fuses or breakers in a breaker box. It is also desirable to design a similar device for a gas pipeline that allows the gas to flow under normal operating conditions, but which shuts off the flow of natural gas or LP gas when there is an excess flow rate either because of a malfunctioning appliance or because of a catastrophic break in the pipeline.
One example of where a catastrophic break occurs in a fluid line is where a motorist inadvertently drives away from a gas pump or an LP gas supply tank before removing the nozzle or LP gas fitting. When this happens, gasoline is usually spilled on the ground or LP gas is discharged into the air, either of which creates an environmental hazard and a fire hazard. In this example, it is desirable that a device shut off the flow of fluid before either very much gasoline is spilled on the ground or LP gas is discharged into the atmosphere.
It is to solving these problems and others that the present invention is directed.